Mixing and diluting are essential steps in many assay procedures and constitute important unit operations for lab on a chip or other microfluidic platforms. In particular for point of care applications, mixing and diluting methods need to be fast. In contrast to macroscopic systems where liquid mixing can be achieved by external means such as stirring, shaking or other methods of promoting turbulence in the liquid system, mixing in microfluidic systems is more challenging. Due to the small characteristic dimensions of microfluidic devices the flow is typically laminar and microfluidic mixers have to rely on diffusion and chaotic advection. Several microfluidic mixing principles have been introduced in the past (see, for example, N. T. Nguyen, S. Wu, J. Micromech. Microeng., vol. 15 R1-R16, 2005; A. P. Sudarsan, V. M. Ugaz, PNAS, vol. 103, pp. 7228-7233, 2006). Among these mixers are lamination mixers where liquids are laminated in a common channel to decrease diffusion distances. Mixing can be further enhanced by placing obstacles in the channel or introducing curvatures and abrupt changes in the cross sectional-area of the channels to promote chaotic advection or vortex mixing. Other mixers, especially suited for centrifugal microfluidics explore the coriolis force present in a rotating system to induce secondary flows and promote mixing (see for example S. Haeberle et al, Chem. Eng. Technol., vol. 28, pp. 613-616. 2005) or use periodically changing angular accelerations to perform batch mixing (see for example M Grumann et al, Lab Chip, vol. 5, pp. 560-565, 2005).